Conventionally, a stepping motor has a very small air gap between a rotor and a stator, and the rotor and stator are made of rotor core sheets and stator core sheets, respectively. When the rotor core sheet and the stator core sheet are produced from one magnetic metal sheet, small metal clippings are formed in narrow gaps between the rotor core sheet and the stator core sheet. The metal clippings may be broken during a punching operation and not drop into a downside of a die (female die), a part of a die device. And, the punching operation may have to be performed again to remove the metal clippings. What is worse, the die device may be damaged due to clogging of scraps including the metal clippings. In addition, when the rotor core sheet and the stator core sheet are produced from one magnetic metal sheet concentrically (i.e., in a manner that axes of the rotor core sheet and the stator core sheet are aligned with each other), if magnetic pole teeth located radially inward of the stator core sheet can not be punched out in desired shapes, then the rotor core sheet and the stator core sheet need to be punched out with different punches and dies. This results in a low material yield and a high cost.
As an example of the conventional art to solve the above problems, Patent Literature 1 discloses a thin section provided in at least one of the rotor core sheet and the stator core sheet. The thin section is formed by coining and evenly elongating at least one of the core sheets in a thickness direction thereof. With this technique, both of the rotor core sheet and the stator core sheet can be punched out from one magnetic metal sheet using one die device.